Converseen is an image converter and resizer written in C++ with the powerful Qt4 libraries. Thanks to the Magick++ image libraries, it supports more than 100 image formats like DPX, EXR, GIF, JPEG, JPEG-2000, PhotoCD, PNG, Postscript, SVG, TIFF, and many others. Converseen allows you to convert, resize, rotate, and automatically flip an unlimited number of images. It can save you time because it can process more than one image with one mouse click. It features a very simple user interface without strange options.

simpleimageviewer4j is easy-to-use library which provides a simple way to display images in Java (using Swing) to aid in debugging applications which manipulate images. It is also available via the Maven Central Repository for easy inclusion in projects built using Maven.

Marvin is an extensible image processing framework
for Java. It provides features to manipulate
images, to manipulate captured video frames, and
to process images with multi-threading. Its
features can be extended via plug-ins. Plug-ins
can be integrated with the graphical user
interface, and their plug-in performance can be
analyzed. Every image processing algorithm is
developed as a plug-in that can be plugged into
the MarvinEditor, an image manipulation program
that uses plug-ins developed using Marvin, or into
third-party applications. Currently there are 55
plug-ins available.

Mahotas is an image processing library for Python. It includes a couple of algorithms implemented in C++ for speed while operating in numpy arrays. The main algorithms are watershed and Otsu thresholding.

LibRaw-demosaic-pack-GPL2 is a set of additional demosaic and noise reduction algorithms for LibRaw. These algorithms include AFD, LMMSE by Manuel Llorens, VCD, modified VCD, AHD+VCD, and two advanced median filters by Paul Lee.

Thumbnailator is a thumbnail generation library with a fluent interface for Java. It simplifies the process of producing thumbnails from existing image files and image objects by providing an API which allows for fine tuning of thumbnail generation, while keeping the amount of code that needs to be written to a minimum.

The Common Pipeline Library provides a highly robust set of functions for manipulating signals and images. It is primarily intended for the building of VLT instrument pipelines, but is also useful for generic data handling. It includes a number of useful low-level data types, medium-level data access methods, standard implementations of commonly-used signal processing and data reduction tasks, and dynamic loading of "recipes" for data processing.

imread is a simple library which reads and saves images from disk to and from numpy arrays. Its goal is to perform this task simply, so that it can become very stable, leaving more complex image processing for other packages.